9 
in turn to another strain of E. coli or other organism if the Iv-12 
cell were accidentally introduced into the intestinal tract? Could 
some DXA recombinant manipulation produce novel E. coll cells 
which would be pathogenic or ecologically disruptive? Could genes 
from higher organisms be transferred to any of the prokaryotic cells 
(cells without a typical nucleus, such as E. coll, or other bacteria or 
algae) and be expressed in such a way as to cause harm ? Is it possible 
to construct a host cell for recombinant DXA research which would 
be so fastidious in its growth requirements that it could not grow 
outside the laboratory ? 
Creation of a novel 'pathogenic E. c.oli 
The Academy panel's conclusions, while not absolute, indicate a 
negligible risk of creating a novel pathogenic E. coli in experiments 
with the Iv-12 strain host cell and special variants developed specif- 
ically for recombinant DXA work. The Iv-12 strain lacks the genetic 
capability to synthesize an important substance involved in the patho- 
genicity of other strains of E. coll. The K-12 strain cannot establish 
itself as a resident organism in the human intestine and does not mul- 
tiply in that environment. Iv-12 is therefore a “safe” research host 
cell without any modification to reduce further its survival 
capabilities. 
The panel based these judgments in part on the conclusions of a 
meeting of microbiologists and epidemiologists at Falmouth. Mass., 
in June 1977. 1 The conference reviewed a vai'iety of experimental 
findings including the following: 
E. coli Iv-12 cannot be converted into an epidemic pathogen by 
laboratory manipulations with DXA inserts. 
Deliberate attempts to induce virulence in Iv-12 by inserting 
genes known to regulate virulence factors in other wild strains of 
E. coli failed to produce a fully pathogenic strain of K-12. These 
experiments used standard genetic methods rather than DXA 
recombinant techniques. 
K-12 deliberately fed to human volunteers soon disappears 
from the human intestine; in one case limited colonization oc- 
curred but did not persist beyond 6 days. The human body defense 
mechanisms are very effective against K-12; the strain is easily 
destroyed by normal chemical activities in the intestine. 
A deliberate attempt to produce a hybrid of Iv-12 and Shigella 
fexreri . an organism which can produce infection in the bowel, 
resulted in a hybrid that picked up genes from Shigella but failed 
to produce any disease and quickly disappeared from the intestines 
of volunteers who ingested it. 
The special nontransmissible plasmids used in recombinant 
DXA work with K-12 cannot be spread to other host bacteria 
within the human intestine. 
An attempt to produce a virulent K-12 by transfer of plasmids 
from naturally occurring E. coli strains was unsuccessful. 
Taken together, these results suggest that K-12 cannot be made 
pathogenic by processes which convert other varieties of E. coli. 
1 The proceedings of the Falmouth conference are published in the Journal of Infectious 
Diseases, vol. 137, May 197S, pp. 613-714. 
[Appendix B — 269] 
